Peromyscines are the most widely distributed and abundant native North American mammals. Recently Peromyscus leucopus and P maniculatus abruptly rose to national attention when they were discovered to be the primary reservoirs of microbes causing two emerging infectious diseases: Lyme disease and Hantaviral pulmonary syndrome. Aptly called "The Drosophila of North American Mammology" peromyscines are also considered to be an ideal model for studying 1) the genes responsible for reproductive isolation and speciation, and 2) the genes enabling the physiological and behavioral adaptation to changing environmental conditions, adaptation to other species, adaptation to each other, and adaptation to microbial and other parasites. An important tool for exploiting this potential is a linkage map. It is the Aim of this proposal to develop an intermediate-density linkage map of P maniculatus bairdii using PCR based markers at sufficient density, approximately 5-10 cM, to permit identification of major segments syntenic with the reference species, Mus musculus. Such markers consist of 1) Type I (Protein Coding Genes) important for synteny identification, and 2) Type II (Microsatellites), which are highly polymorphic and will ultimately be used for QTL analysis. The linkage analysis panel was selected for maximizing utilizable polymorphism and is composed of Interspecific Meiotic Segregants of crosses between the sister species P m bairdii and P polionotus. Development of a Peromyscus linkage map will markedly improve the research potential of the species, enhancing projects currently underway and encouraging the development of other projects that explore the genetics of host-parasite interactions, speciation, behavior and the various aspects of adaptive trait acquisition. Specific information enabled by such a map includes QTL analysis, genetic manipulation and dissection of individual QTLs, and identification of potential candidate genes for individual QTLs.